The known techniques for analysing the structure and chemical composition of bones consist in performing an X-ray or analysing ultrasound echo scan. The techniques using X-ray are distinguished by a very good specificity and sensitivity at 95% level in the case of a dual energy X-ray densitometry (absorptiomerty) method but they are time-consuming and troublesome/inconvenient. They involve exposing a patient to a harmful effect of X-ray and require using expensive sizeable equipment. The ultrasound methods are not very reliable as they are based on a measurement of mechanical properties of the bones which do not reflect the structure and chemical composition accurately.
A method for analysing bone structure described in the British Patent GB2449226 relates to bio-impedance spectroscopic measurements using an apparatus equipped with two measuring electrodes. The method consists in generating, with a use of a generator, at least one standard signal of a defined waveform which is applied to the bone tissue through the surrounding tissues, skin and muscles and then the electrical response which is a difference of potentials caused by current flowing through the analysed tissues is directed to the measuring system using the same electrodes. The data related to the bone tissue structure are generated in the system.
The apparatus consists of two electrodes connected to a generator of changeable, arbitrarily selected frequency standard ac current signal and a system monitoring electrical response of a measuring circuit with a computer generating output data. Both electrodes are used simultaneously for supplying the current and monitoring the response concerning the bone tissue density. This method allows to perform a quick, non-invasive and harmless bio-impedance measurement. However, it does not provide the possibility of distinguishing from bio-impedance signal the information describing electrical parameters of bone tissue alone, especially its spongy part which was intended to be the subject of analysis by the inventors of the quoted solution. This method does not distinguish that the vast majority of measuring current flows through the tissues surrounding the bones, i.e., muscles, fat tissue and skin which, in this case, are insignificant from diagnostic point of view. In addition, this method does not compensate for screening effect of the outer bone surface which is characterized by high impedance, which might decrease considerably the measuring current flowing through the inner bone structures.